Toy building block set

ABSTRACT

A toy building block set includes a socket block piece and at least one of first and second plug block pieces. The socket block piece has a socket wall body and at least one engaging hole of a regular polygonal shape. Each of the first and second plug block pieces has a plug body and at least one polygonal insert plug configured to be inserted into and in frictional engagement with the engaging hole with a first frictional force to permit rotation of the plug block piece relative to the socket block piece by a forcible torque and to keep a predetermined angle of the plug block piece relative to the socket block piece when the forcible torque is removed. The plug body is partially inserted into and in frictional engagement with the engaging hole with a second frictional force larger than the first frictional force.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Patent Application No.108102032, filed on Jan. 18, 2019.

FIELD

The disclosure relates to a toy building block set, and moreparticularly to a toy building block set in which two block pieces areinterlockable at a variety of angular positions.

BACKGROUND

In a conventional toy building block set, two identical block pieces areusually interlocked at several angular positions, such as 0, 90 and 180degrees, which limits the configuration of combination and hence rendersuse of the toy monotonous.

SUMMARY

Therefore, an object of the disclosure is to provide a toy buildingblock set that can alleviate at least one of the drawbacks of the priorart.

According to the disclosure, the toy building block set includes asocket block piece and at least one of first and second plug blockpieces. The socket block piece has a socket wall body and at least oneengaging hole which is formed in the socket wall body and bordered by aninner peripheral wall that surrounds a rotating axis normal to thesocket wall body. The inner peripheral wall has a cross-section which isof a regular polygonal shape. Each of the first and second plug blockpieces has a plug body and at least one polygonal insert plug whichextends from the plug body. The polygonal insert plug has an outerperipheral wall with a cross-section which is of a regular polygonalshape to be inserted into the engaging hole in an extending directionparallel to the rotating axis and in frictional engagement with theinner peripheral wall with a first frictional force that is dimensionedto permit rotation of the plug block piece relative to the socket blockpiece about the rotating axis by a forcible torque and to keep apredetermined angle of the plug block piece relative to the socket blockpiece when the forcible torque is removed. The plug body is partiallyinserted into the engaging hole and in frictional engagement with theinner peripheral wall with a second frictional force which is largerthan the first frictional force.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent inthe following detailed description of the embodiments with reference tothe accompanying drawings, of which:

FIG. 1 is a perspective view illustrating a first embodiment of a toybuilding block set according to the disclosure in an interlocked state;

FIG. 2 is a perspective view illustrating the first embodiment;

FIG. 3 is a fragmentary sectional view illustrating a plug block pieceinterconnecting two socket block pieces of the first embodiment;

FIG. 4 is a fragmentary sectional view illustrating another plug blockpiece interconnecting two socket block pieces of the first embodiment;

FIG. 5 is a fragmentary sectional view similar to FIG. 4, but taken fromanother angle;

FIGS. 6 to 8 are schematic front views illustrating rotation of twosocket block pieces relative to each other;

FIG. 9 is a perspective view illustrating a second embodiment of a toybuilding block set according to the disclosure in an interlocked state;

FIG. 10 is a perspective view similar to FIG. 9, but taken from anotherangle;

FIG. 11 is a perspective view of the second embodiment;

FIG. 12 is a perspective view similar to FIG. 11, but taken from anotherangle;

FIG. 13 is a perspective view illustrating a third embodiment of a toybuilding block set according to the disclosure in an interlocked state;

FIG. 14 is a perspective view of the third embodiment; and

FIGS. 15 and 16 are schematic top views illustrating the thirdembodiment upon actuation of a control unit to rotate two turningmechanisms.

DETAILED DESCRIPTION

Before the disclosure is described in greater detail, it should be notedthat where considered appropriate, reference numerals or terminalportions of reference numerals have been repeated among the figures toindicate corresponding or analogous elements, which may optionally havesimilar characteristics.

Referring to FIGS. 1 and 2, a first embodiment of a toy building blockset 100 according to the disclosure includes three socket block pieces1, a first plug block piece 2 and a second plug block piece 2′. Each ofthe socket and plug block pieces 1, 2, 2′ is made from a plasticmaterial.

With reference to FIGS. 3 to 5, each socket block piece 1 has a socketwall body 11 in the form of an elongated plate, and three engaging holes12 which are formed in the socket wall body 11 and spaced apart fromeach other in a lengthwise direction of the socket wall body 11. Each ofthe engaging holes 12 is bordered by an inner peripheral wall thatsurrounds a rotating axis normal to the socket wall body 11, i.e.,transverse to the lengthwise direction. The number of the engaging holes12 of each socket block piece 1 may be varied, such as one, two or atleast four engaging holes 12. In this embodiment, each of the engagingholes 12 penetrates through the socket wall body 11. Alternatively, theengaging holes 12 may be blind holes. The inner peripheral wall of eachengaging hole 12 has a cross-section which is of a regular polygonalshape, such as an octagonal shape in this embodiment.

Each of the first and second plug block pieces 2, 2′ is disposed tointerconnect two adjacent ones of the socket block pieces 1. The firstplug block piece 2 has a plug body 21 and two polygonal insert plugs 22which extend from two ends of the plug body 21 and opposite to eachother. The polygonal insert plugs 22 are respectively inserted into theengaging holes 12 of two adjacent ones of the socket block pieces 1. Thesecond plug block piece 2′ has a plug body 21′, a polygonal insert plug22 which extends from an end of the plug body 21′, and a circular insertplug 23 which extends from the other end of the plug body 21′ and awayfrom the polygonal insert plug 22. The polygonal and circular insertplugs 22, 23 are respectively inserted into the engaging holes 12 of twoadjacent ones of the socket block pieces 1. Specifically, the polygonalinsert plug 22 has an outer peripheral wall with a cross-section whichis of a regular polygonal shape, such as an octagonal shape, to beinserted into the engaging hole 12 in an extending direction parallel tothe rotating axis and in frictional engagement with the inner peripheralwall with a first frictional force that is dimensioned to permitrotation of the plug block piece 2, 2′ relative to the socket blockpiece 1 about the rotating axis by a forcible torque and to keep apredetermined angle of the plug block piece 2, 2′ relative to the socketblock piece 1 when the forcible torque is removed. In this embodiment,the predetermined angle may be 0, 45, 90, 135 or 180 degrees.Alternatively, the cross-section of the polygonal insert plug 22 and theengaging hole 12 may be of another polygonal shape, such as a regulartriangular shape, a regular pentagonal shape, a regular heptagonalshape, etc. The circular insert plug 23 has an outer peripheral wallwith a cross-section which is of a circular shape to be inserted intothe engaging hole 12 in the extending direction and in frictionalengagement with the inner peripheral wall with a third frictional forcethat is dimensioned to permit rotation of the second plug block piece 2′relative to the socket block piece 1 about the rotating axis by aforcible torque and to keep any angle of the plug block piece 2′relative to the socket block piece 1 when the forcible torque isremoved. The plug body 21, 21′ of each of the first and second plugblock pieces 2, 2′ is partially inserted into the engaging hole 12 whenthe polygonal or circular insert plug 22, 23 is inserted into theengaging hole 12, and is in frictional engagement with the innerperipheral wall with a second frictional force which is larger than thefirst frictional force or the second frictional force.

In this embodiment, each of the first and second plug block pieces 2, 2′has two insert plugs 22 or 22, 23 to interconnect two of the socketblock pieces 1. Alternatively, each plug block piece 2, 2′ may have onlyone insert plug 22 or 23. In this embodiment, the insert plugs 22 of thefirst plug block piece 2 are configured to be aligned with each other inthe extending direction such that the two socket block pieces 1interlocked by the first plug block piece 2 are kept relative to eachother at an angular position by an included angle of 0, 45, 90, 135 or180 degrees. The two socket block pieces 1 interlocked by the secondplug block piece 2′ are kept relative to each other at an angularposition by any included angle of 0 to 180 degrees. Each the first andsecond plug block pieces 2, 2′ also has a tubular hole 24 which extendsthrough the plug body 21, 21′ and the polygonal insert plugs 22 or thepolygonal and circular insert plugs 22, 23 in the extending direction.Each of the first and second plug block pieces 2, 2′ also has aplurality of splits 25 which are formed in and extend through the outerperipheral wall of the polygonal or circular insert plug 22, 23 to be incommunication with the tubular hole 24 and angularly displaced from eachother so as to permit resilient engagement of the outer peripheral wallwith the inner peripheral wall of the socket block piece 1 and so as tofacilitate insertion of the polygonal or circular insert plug 22, 23into the engaging hole 12. With the splits 25, the polygonal or circularinsert plug 22, 23 is rotatably inserted into the engaging hole 12 topermit rotation of the first or second plug block piece 2, 2′ relativeto the socket block piece 1 to adjust the included angle therebetween,as shown in FIGS. 6 to 8. Specifically, the two socket block pieces 1interlocked by the polygonal insert plug 22 of the first plug blockpiece 2 can be rotated relative to each other about the rotating axis tohave an included angle of 0, 45, 90, 135 or 180 degrees. The two socketblock pieces 1 interlocked by the circular insert plug 23 of the secondplug block piece 2′ can be rotated relative to each other about therotating axis to have any included angle of 0 to 180 degrees. Forexample, the socket block pieces 1 may be formed as limb parts of arobot (not shown), and the first and second plug block pieces 2, 2′ maybe formed as joints of the limb parts. Moreover, in this embodiment, thetubular hole 24 has a cross-section of a dodecagonal shape for a stem(not shown) having a regular hexagonal cross-section to be insertedthereinto by two different angles.

Specifically, referring to FIGS. 2 and 3, the inner peripheral wall ofeach engaging hole 12 has a middle wall portion 121 extending in adirection of the rotating axis, two larger-diameter wall portions 122respectively extending from two ends of the middle wall portion 121, andtwo shoulder portions 123 each interposed between the middle wallportion 121 and a respective one of the larger-diameter wall portions122. In this embodiment, each of the middle and larger-diameter wallportions 121, 122 has a cross-section of a regular octagonal shape. Eachof the polygonal and circular insert plugs 22, 23 has a plurality offlange sections 221, 231 formed at a terminal end thereof. When thepolygonal or circular insert plug 22, 23 is inserted into the engaginghole 12, the flange sections 221, 231 are received within onelarger-diameter wall portion 122 and abut against the correspondingshoulder portion 123, and the plug body 21 is partially received withinthe other larger-diameter wall portion 122 and abuts against thecorresponding shoulder portion 123. Thus, the polygonal or circularinsert plug 22, 23 can be firmly engaged in the engaging hole 12. Inthis embodiment, the plug body 21 has a regular octagonal cross-sectionto match with the larger-diameter wall portion 122 so as to preventrotation of the first plug block piece 2 relative to the socket blockpiece 1 when the plug body 21 is partially inserted into the engaginghole 12. The plug body 21′ is circular in cross-section so as to renderthe second frictional force larger to prevent rotation of the secondplug block piece 2′ relative to the socket block piece 1. Moreover, eachof the socket block piece 1 has two surrounding flange walls 13 formedat two sides of the socket wall body 11 and surrounding the engagingholes 12 for concealing the plug bodies 21, 21′ of the first and secondplug block pieces 2, 2′ when the first and second plug block pieces 2,2′ are disposed to interconnect two socket block pieces 1. Furthermore,each polygonal insert plug 22 has a plurality of ribs 222 which are infrictional engagement with the inner peripheral wall of the engaginghole 12 to increase the friction therebetween.

Referring to FIGS. 9 to 12, in a second embodiment, the toy buildingblock set 100 includes two socket block pieces 1′, a first plug blockpiece 2″, a second plug block piece 2′, and a retaining piece 3. Each ofthe socket block pieces 1′ has five of the engaging holes 12. Eachlarger-diameter wall portion 122 of the inner peripheral wall of eachengaging hole 12 has a plurality of slots 124 angularly spaced apartfrom each other and each extending in the direction of the rotatingaxis. The plug body 21″ of the first plug block piece 2″ has a pluralityof keys 211 formed thereon and angularly spaced apart from each other tobe respectively engaged in the slots 124 so as to prevent rotation ofthe first plug block piece 2″ relative to the socket block piece 1′. Inthis embodiment, eight of the slots 124 are formed in thelarger-diameter wall portion 122. Eight of the keys 211 are formed onthe plug body 21″ of the first plug block piece 2. The retaining piece 3has a retaining shank 32 which extends to be inserted into the tubularhole 24 of the first plug block piece 2″ in the extending direction fromone polygonal insert plug 22 when the polygonal insert plug 22 isinserted into the engaging hole 12 so as to decrease resilientdeformation of the polygonal insert plug 22, and a round-disc shapedhead 31 which is disposed on and extends radially and outwardly from anend of the retaining shank 32 to abut against the polygonal insert plug22 and be received in the larger-diameter wall portion 122 of theengaging hole 12. The retaining piece 3 further has a plurality offilling ribs 321 which are formed on the retaining shank 32 to berespectively filled in the splits 25 when the retaining shank 32 isinserted into the tubular hole 24. With the retaining shank 32 and thefilling ribs 321 disposed to decrease the resilient deformation of thepolygonal insert plug 22, the first plug block piece 2″ is retainedfirmly to the socket block piece 1′ for preventing rotation relative toand removal from the engaging hole 12. In this embodiment, the secondplug block piece 2′ has the polygonal insert plug 22 retained to onesocket block piece 1′, and the circular insert plug 23 rotatably engagedwith the other socket block piece 1′. The retaining piece 3 can be alsodisposed to be inserted into the tubular hole 24 of the second plugblock piece 2′ or the first plug block piece 2 in the first embodiment.

Referring to FIGS. 13 to 16, in a third embodiment, the toy buildingblock set 100 is assembled as a toy vehicle, and includes a main vehicleframe 10, two turning mechanisms 20, a control unit 30, two rear wheels40 and two motors 50.

The turning mechanisms 20 are disposed at two sides of a front end ofthe main vehicle frame 10. Each turning mechanism. 20 includes a fixedblock piece 1″, two adaptor block pieces 4, two socket block pieces 1,four second plug block pieces 2′, a front wheel 201 and a rotating shaft5.

The fixed block piece 1″ is fixed on the front end of the main vehicleframe 10, and has a wall body 11′ of a C-shaped configuration, and twoengaging holes 12 formed in two terminal ends of the wall body 11′. Eachadaptor block piece 4 has a curved wall body 41, an adaptor engaginghole 42 and an adaptor insert plug 43. The curved wall body 41 has firstand second wall segments 411, 412 extending transverse to each other.The adaptor engaging hole 42 is formed in the first wall segment 411 andconfigured to be engaged with a polygonal insert plug 22 of the secondplug block piece 2′ (or a polygonal insert plug 22 of the first plugblock piece 2 in the previous embodiment). The adaptor insert plug 43projects from the second wall segment 412 and is configured to beengaged in an engaging hole 12 of the socket block piece 1.Specifically, the adaptor engaging hole 42 has a cross-section of aregular polygonal shape to allow insertion and frictional engagement ofthe polygonal insert plug 22 of the second plug block piece 2′ (or thefirst plug block piece 2). The extending direction of the adaptor insertplug 43 is transverse to the inserting direction of the adaptor engaginghole 42. The adaptor insert plug 43 has a cross-section of a regularpolygonal shape to be inserted into and frictionally engaged with theengaging hole 12 of the socket block piece 1. The adaptor insert plug 43has a configuration similar to that of the polygonal insert plug 22.Alternatively, the extending direction of the adaptor insert plug 43 maybe not transverse to the inserting direction of the adaptor engaginghole 42. Still alternatively, the adaptor insert plug 43 may have across-section of a circular shape and may be similar to the circularinsert plug 23 in configuration. The adaptor engaging holes 42 of theadaptor block pieces 4 are disposed inboard of the C-shaped wall body11′ of the fixed block piece 1″ and respectively aligned with theengaging holes 12 of the fixed block piece 1″. Two of the second plugblock pieces 2′ are disposed to interconnect each adaptor block pieceand the fixed block piece 1″. Specifically, the polygonal and circularinsert plugs 22, 23 of the second plug block piece 2′ are respectivelyengaged in the aligned adaptor engaging hole 42 and the engaging hole 12so as to allow rotation of the adaptor block piece 4 relative to thefixed block piece 1″. One of the socket block pieces 1 erects and hasupper and lower engaging holes 12 respectively engaged with the adaptorinsert plugs 43 of the adaptor block pieces 4, and a middle engaginghole 12 aligned with an axial hole (201 a) in the front wheel 201. Oneof the second plug block pieces 2′ is disposed to interconnect thesocket block piece 1 and the front wheel 201 to have the polygonalinsert plug 22 engaged with the middle engaging hole 12 of the socketblock piece 1, and the circular insert plug 23 engaged with the axialhole (201 a) of the front wheel 201 to allow rotation of the front wheel201 relative to the socket block piece 1 for rolling on a supportsurface (not shown). The other one of the socket block pieces 1 isplaced horizontally above the fixed block piece 1″, and has an engaginghole 12 aligned with the engaging hole 12 of the fixed block piece 1″.The polygonal insert plug 22 of one second plug block piece 2′ isengaged in the engaging hole 12 of the socket block piece 1. Therotating shaft 5 has a cross-section of a polygonal shape, such as aregular hexagonal shape, and is made from a copper material. Therotating shaft 5 is configured to be inserted into the tubular holes 24of the three aligned second plug block pieces 2′ so as to operativelydrive rotation of the second plug block pieces 2′ with the rotatingshaft 5 about the rotating axis. Thus, when the horizontal socket blockpiece 1 above the fixed block piece 1″ is rotated relative to therotating shaft 5, the adaptor block pieces 4 are driven to rotate aboutand relative to the rotating shaft 5 so as to turn the front wheel 201and the upright socket block piece 1 about the rotating shaft 5 toperform turning of the front wheel 201.

The control unit 30 has an elongated socket block piece 1′ and twosecond plug block pieces 2′. The socket wall body 11 of the elongatedsocket block piece 1′ is in the form of an elongated plate which extendsin an elongated direction and is longer than the socket block piece 1 ofthe first embodiment, and has a plurality of the engaging holes 12 whichare spaced apart from each other along the elongated direction. Two ofthe engaging holes 12 at two ends thereof are respectively aligned withthe rear engaging holes 12 of the horizontal socket block pieces 1 ofthe turning mechanisms 20. The polygonal insert plugs 22 of the twosecond plug block pieces 2′ are respectively engaged in the rearengaging holes 12 of the horizontal socket block pieces 1 of the turningmechanisms 20, and the circular insert plugs 23 thereof are respectivelyengaged in the end engaging holes 12 of the elongated socket block piece1′ so as to allow rotation of the elongated socket block piece 1′″relative to the horizontal socket block pieces 1 of the turningmechanisms 20. Thus, as shown in FIGS. 15 and 16, when the elongatedsocket block piece 1″ is actuated to move transversely, the horizontalsocket block pieces 1 of the turning mechanisms 20 are rotated relativeto the rotating shafts 5 so as to turn the front wheels 201. Forexample, the control unit 30 may have an actuating unit (not shown) toactuate the movement of the elongated socket block piece 1 so as tocontrol the turning of the front wheels 201.

The rear wheels 40 are disposed at two sides of a rear end of the mainvehicle frame 10. The motors 50 are disposed on the main vehicle frame10 to respectively drive the rear wheels 40 to move forwards the toyvehicle.

As illustrated, with the engaging holes 12 of a regular polygonal shapeand the polygonal insert plugs 22 configured to be inserted into theengaging holes 12, rotation of the plug block pieces relative to thesocket block pieces is allowed and can keep a predetermined angle of theplug block pieces relative to the socket block pieces for playing andusing the toy building block set with more variety.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent, however, to oneskilled in the art, that one or more other embodiments may be practicedwithout some of these specific details. It should also be appreciatedthat reference throughout this specification to “one embodiment,” “anembodiment,” an embodiment with an indication of an ordinal number andso forth means that a particular feature, structure, or characteristicmay be included in the practice of the disclosure. It should be furtherappreciated that in the description, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure and aiding in theunderstanding of various inventive aspects.

While the disclosure has been described in connection with what areconsidered the exemplary embodiments, it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. A toy building block set comprising: a socketblock piece having a socket wall body and at least one engaging holewhich is formed in said socket wall body and bordered by an innerperipheral wall that surrounds a rotating axis normal to said socketwall body, said inner peripheral wall having a cross-section which is ofa regular polygonal shape; and at least one of first and second plugblock pieces having a plug body and at least one polygonal insert plugwhich extends from said plug body, said polygonal insert plug having anouter peripheral wall with a cross-section which is of a regularpolygonal shape to be inserted into said engaging hole in an extendingdirection parallel to the rotating axis and in frictional engagementwith said inner peripheral wall with a first frictional force that isdimensioned to permit rotation of said plug block piece relative to saidsocket block piece about the rotating axis by a forcible torque and tokeep a predetermined angle of said plug block piece relative to saidsocket block piece when the forcible torque is removed, said plug bodybeing partially inserted into said engaging hole and in frictionalengagement with said inner peripheral wall with a second frictionalforce which is larger than the first frictional force.
 2. The toybuilding block set as claimed in claim 1, wherein said engaging holepenetrates through said socket wall body.
 3. The toy building block setas claimed in claim 2, wherein said first plug block piece has two ofsaid polygonal insert plugs which extend from said plug body and awayfrom each other.
 4. The toy building block set as claimed in claim 2,wherein said second plug block piece has a circular insert plug whichextends from said plug body and away from said polygonal insert plug,said circular insert plug having an outer peripheral wall with across-section which is of a circular shape to be inserted into saidengaging hole in the extending direction and in frictional engagementwith said inner peripheral wall with a third frictional force that isdimensioned to permit rotation of said second plug block piece relativeto said socket block piece about the rotating axis by a forcible torqueand to keep any angle of said second plug block piece relative to saidsocket block piece when the forcible torque is removed, and that issmaller than the second frictional force.
 5. The toy building block setas claimed in claim 2, wherein said at least one of said first andsecond plug block pieces has a tubular hole which extends through saidplug body and said polygonal insert plug in the extending direction. 6.The toy building block set as claimed in claim 5, wherein said at leastone of said first and second plug block pieces has a plurality of splitswhich are formed in and extend through said outer peripheral wall to bein communication with said tubular hole and are angularly displaced fromeach other so as to permit resilient engagement of said outer peripheralwall with said inner peripheral wall of said socket block piece.
 7. Thetoy building block set as claimed in claim 6, further comprising aretaining piece which has a retaining shank that extends to be insertedinto said tubular hole in the extending direction to decrease resilientdeformation of said polygonal insert plug, and a head that is disposedon and extends radially and outwardly from an end of said retainingshank to abut against said polygonal insert plug.
 8. The toy buildingblock set as claimed in claim 7, wherein said retaining piece has aplurality of filling ribs which are formed on said retaining shank to berespectively filled in said splits when said retaining shank is insertedinto said tubular hole.
 9. The toy building block set as claimed inclaim 5, further comprising a rotating shaft which is configured to beinserted into said tubular hole of said at least one of said first andsecond plug block pieces so as to operatively drive rotation of said atleast one of said first and second plug block pieces relative to saidsocket block piece about the rotating axis.
 10. The toy building blockset as claimed in claim 9, wherein each of said tubular hole and saidrotating shaft has a cross-section of a polygonal shape.
 11. The toybuilding block set as claimed in claim 1, further comprising an adaptorblock piece, said adaptor block piece having a curved wall body, atleast one adaptor engaging hole which is formed in said curved wall bodyand which has a cross-section of a regular polygonal shape to allowinsertion and frictional engagement of said polygonal insert plug ofsaid at least one of said first and second plug block pieces, and atleast one adaptor insert plug which projects from said curved wall bodyand which has a cross-section of a regular polygonal or circular shapeto be inserted into and frictionally engaged with said engaging hole ofsaid socket block piece.
 12. The toy building block set as claimed inclaim 11, wherein extending directions of said adaptor insert plug andsaid adaptor engaging hole are transverse to each other.
 13. The toybuilding block set as claimed in claim 1, wherein said socket wall bodyof said socket block piece is in the form of an elongated plate whichextends in an elongated direction, and has a plurality of said engagingholes which are spaced apart from each other along the elongateddirection.
 14. The toy building block set as claimed in claim 1, whereinsaid cross-section of said polygonal insert plug is octagonal.
 15. Thetoy building block set as claimed in claim 2, wherein said innerperipheral wall of said engaging hole has a middle wall portionextending in a direction of the rotating axis, two larger-diameter wallportions respectively extending from two ends of said middle wallportion, and two shoulder portions each interposed between said middlewall portion and a respective one of said larger-diameter wall portions,said polygonal insert plug of said at least one of said first and secondplug block pieces having a plurality of flange sections formed at aterminal end thereof such that, when said polygonal insert plug isinserted into said engaging hole, said flange sections are receivedwithin one of said larger-diameter wall portions and abut against acorresponding one of said shoulder portions, and said plug body ispartially received within the other one of said larger-diameter wallportions and abuts against a corresponding one of said shoulderportions.
 16. The toy building block set as claimed in claim 15, whereinsaid inner peripheral wall of said engaging hole has a plurality ofslots formed in each of said larger-diameter wall portions and eachextending in the direction of the rotating axis, said plug body of saidat least one of said first and second plug block pieces having aplurality of keys which are formed thereon and angularly displaced fromeach other so as to be engaged with said slots, respectively.